This invention relates to the production of amorphous semiconductors having a specified bandgap, and, more particularly, to amorphous silicon having such a bandgap.
Semiconductors have an extended region of discontinuity in their internal energy levels between their valence and conduction bands. This region of discontinuity is known as a "bandgap". It determines how a device made from the material will respond to external stimuli.
In order to realize the most efficient interchange or interaction between a device and its source of activation, for example, between the solar spectrum and a photo responsive device, it is advantageous to match the bandgap of the device to that of the energizing spectrum. This procedure is analogous to the matching of electrical elements in order to obtain maximum energy transfer.
Unfortunately, previously produced amorphous semiconductors have been characterised by undesirable bandgaps. It has not been possible in the case of silicon, for example, to provide bandgaps that could achieve the most efficient use of the solar spectrum with devices made with the semiconductors.
An object of the invention is to achieve precision control over the bandgaps of amorphous silicon.